Bicycle Fork and Steering Tube

ABSTRACT

A combination bicycle fork and steering tube assembly is formed with a pair of downwardly directed, mutually converging end closure tabs that are bent over into abutment and welded together to define peripherally enclosed fork openings at the ends of the steerer tube. The upper ends of the hollow fork legs are configured to follow the surface contours of the lower end of the steerer tube and are welded to the end closure tabs about the circumferences of the enclosed fork openings at the lower end of the steering tube. The front wheel axle dropouts are formed directly in the lower ends of the fork legs, which include internal dropout support inserts. The dropout support inserts are sandwiched in between a pair of flat, mutually parallel dropout tabs defined directly in the lower ends of the fork legs.

CROSS-REFERENCES TO RELATED APPLICATIONS

This patent application is a continuation and claims the benefit of U.S.patent application Ser. No. 11/488,404 filed Jul. 19, 2006 for BicycleFork and Steering Tube, which application is incorporated here by thisreference.

TECHNICAL FIELD

This invention relates to a bicycle fork and steering tube constructionwith particular application to BMX bicycles.

BACKGROUND ART

Bicycles have historically be constructed with a cylindrical steerertube having an upper end joined to the bicycle handlebars, and a lowerend to which a bicycle front wheel fork is rigidly fastened. The steerertube is rotatable within a hollow, cylindrical head tube which forms apart of the bicycle frame and which is located at the front of thebicycle frame. The rider rotates the steerer tube by turning thehandlebars to the left or right in order to turn the front wheel fork tothe left or right. By altering the orientation of the front wheelrelative to the bicycle frame, the rider is able to change the directionof travel of the bicycle to the left or right as desired.

Conventional bicycle fork and steering tube structures have certaindisadvantages. These disadvantages are particularly pronounced in thecase of BMX bicycles, in which reduced weight and reduced complexity ofconstruction are particularly important. There are several standardbicycle front wheel fork and steerer tube structures that are widelyused in different styles of BMX bicycles.

One prevalent type of bicycle front wheel fork and steerer tubecombination is known as the “unicrown” fork. Bicycle forks of this typeare comprised of bent tubular fork legs welded directly to the hollow,cylindrical steerer tube. In this type of bicycle fork and steerer tubeconstruction the steerer tube is simply cut off at right angles at itslower end and the fork legs are mitered to meet the sides of theopen-ended steerer tube.

The “unicrown” configuration results in a open hole at the base of thesteerer tube of the finished fork. This open hole can become fouled withdebris that might impede the rotation of the front bicycle wheel thatrotates about the front wheel axis within the fork.

Furthermore, this structure allows for relatively large, localizeddeformations under loads, thus resulting in metal fatigue and ultimatelymetal failure. To avoid metal fatigue, heavy wall thickness is requiredin both the steerer tube and the fork legs. As a result, the finishedbicycle front wheel fork and steering tube combination is excessivelyheavy.

In order to mount the front bicycle wheel between the fork legs, dropoutflanges are typically welded to the lower extremities of the fork legs.These dropout flanges are formed as solid plates, castings, or forgingswelded to the end or side of each fork leg.

That is, the dropout flanges project in planes parallel to each otherthat are both perpendicular to the plane of alignment of the legs of thebicycle fork. Due to the off center stresses that result from torqueforces acting relative to the plane of alignment of the fork legs, theentire lower fork assembly, specifically the fork legs, the dropoutflanges and the welds that join the dropout flanges to the lower ends ofthe fork legs must be very sturdy and are unduly heavy. Lighter weightdropout flanges tend to be thinner and significantly weaker thandesired.

Also, in the field of BMX bicycle forks and steerer tubes it is oftennecessary to run a front brake cable down the center of the steerer tubein order to activate the front brake while avoiding contact between thebrake cable and the frame when the steering system is rotated more thanone hundred eighty degrees. The brake cable passage created conflictswith the “top bolt” which is required for setting up the headset thatholds the bicycle handlebars and which bears tension.

The conventional way of routing the brake cable is to run it through thecenter of a hollow bolt having external hexagonal wrench flats thataccommodate a wrench for tensioning the bolt. That is, the conventionalhollow bolt system relies upon a large, external hexagonal configurationon a low bolt head or a smaller hex head that protrudes upwardly in anundesirable way. Another common solution to this problem is to use ahexagonal socket head located centrally in the bolt. However, with theprevalent existing standard headset sizes there is insufficient room tokeep a hexagonal socket head central while running the cableeccentrically down through the hollow bolt. A common solution to this isto run the cable through the hexagonal socket itself, but this rendersthe socket head unusable until the brake cable has been removed.Furthermore, with the hex head top bolts most widely utilized, it is notpossible to pass a brake cable assembly through intact.

Therefore, any replacement of headset parts, stem, or frame parts,generally requires a labor intensive disassembly of the front brakecable adjustment setup at the front braking caliper.

DISCLOSURE OF INVENTION

The present invention provides unique, improved construction featuresthat remedy the deficiencies of prior bicycle front wheel fork andsteering tube systems. The invention provides a bicycle with a wheelfork and steering tube assembly that has a superior, weight-reducingconstruction, and which reduces both weight and stress at the lower endof the steerer tube and at the lower ends of the bicycle fork legs.Moreover, a hollow preload bolt is provided that has a much larger cablerouting access passageway than conventional systems.

In one broad aspect the invention may be considered to be a bicycle forkassembly comprising a hollow steerer tube having a lower end at which aheadset bearing seat is formed. Diametrically opposed notches aredefined in the lower end of the steerer tube.

These notches are directed concave upwardly toward the headset bearingseat. The notches thereby define a pair of downwardly directed endclosure tabs therebetween. These end closure tabs narrow from proximatethe head tube seat to distal extremities. The distal extremities of theenclosure tabs are bent in toward each other to meet in mutual abutmentwhere they are rigidly secured together. As a result, the concavenotches define peripherally enclosed fork openings at the lower end ofthe steerer tube.

A pair of hollow, tubular fork legs is provided having upper and lowerends. Each of the fork legs upper ends terminates in a steerer tubeinterface opening having edges that follow the surface contour of thelower end of the steerer tube. These fork leg edges surround the steerertube openings and reside in direct contact with and are welded abouttheir circumferences to the end closure tabs of the steerer tube. Thelower ends of the fork legs terminate in bicycle axle dropouts.

By constructing the interface between the fork legs and the steerer tubein this manner, a potential snag or fouling risk is avoided by closingoff the lower end of the steerer tube. Furthermore, this constructionavoids the excessive weight in the steerer tube that would otherwiseexist due to the extra material within the circumference of the steerertube interface openings at the upper end of the fork legs. By trimmingand forming the lower end of the steerer tube to conform to the areaencompassed within the steerer tube interface openings at the upper endsof the fork legs, a smoother profile results, along with a reduction inweight of the steerer tube. The steerer tube is trimmed to removelightly stressed material that lies within an area that is stiffened bythe welded upper ends of the fork legs.

By notching the lower end of the steerer tube two downwardly projectingend closure tabs are left after trimming of the steerer tube. These tabsare permanently deformed by bending to meet each other and to meet theundersides of the upper ends of the fork legs so that the stresses inthis area are smoothly guided around to the steerer tube.

Material is also left on the steerer tube to form a closed bottom tohelp support the welded upper ends of the fork legs.

In another broad aspect the invention may be considered to be a bicyclefork assembly comprising: a hollow steerer tube having a closed lowerend with a pair of diametrically opposed fork leg openings definedtherein, and a pair of hollow tubular fork legs having upper and lowerends. The upper ends of the fork legs terminate at steerer tubeinterface openings that completely surround the fork leg openings. Theupper ends of the fork legs are welded to the lower end of the steerertube throughout the circumference of the steerer tube interfaceopenings.

The lower ends of each of the fork legs are preferably deformed todefine a pair of flat, mutually parallel dropout tabs disposed in spacedseparation from each other and with dropout notches defined therein.Corresponding downwardly converging interior wall surfaces are alsodefined above the dropout tabs. A dropout support insert is providedthat has a lower dropout reinforcement portion sandwiched in between thedropout tabs. The dropout support insert also has an upper brace portionthat follows the contours of the converging interior wall surfaces ofthe fork legs.

With the construction of the present invention in which the dropouts areformed directly in the lower ends of the tubular fork legs, aconsiderable reduction of weight is achieved. Moreover, by forming thedropouts in the lower ends of the fork legs so they are on the axis ofthe leg tubing, undesirable torsional stresses and other stresses on thefork legs are minimized. The dropout support insert that is employedextends up inside the fork leg to brace the dropout to the tubularportion of the fork leg above it, while also providing support againstdamage and crushing. The construction of the dropout directly in thelower end of each fork leg allows the dropouts to be substantiallythicker, therefore more resistant to bending, while avoiding theaddition of a large amount of excess weight to the bicycle fork andsteering tube assembly.

In still another aspect the invention may be considered to be a bicyclefork assembly comprising: a hollow steerer tube having a lower end andan internally threaded upper end, a pair of hollow, tubular fork legshaving upper ends joined to the lower end of the steerer tube indiametric opposition to each other and lower ends that are configured toform axle dropout slots, and a hollow, cylindrical, annular preloadbolt. The preload bolt has an outer barrel with external threads thereonfor engagement with the internally threaded upper end of the steerertube. The preload bolt has an interior dividing wall that defines anupwardly facing wrench socket radially offset from axial alignment withthe external threads on the barrel. A brake cable routing passage isthereby delineated from the socket within the barrel.

A driving wrench, usually one that is hexagonal in shape, may be engagedin the radially offset wrench socket to rotate the preload bolt totighten or loosen it from the upper end of the steerer tube. By locatingthe socket off center the cross-sectional area of the cable routingpassageway through the hollow preload bolt is increased substantially,and therefore the weight of the preload bolt is reduced. Furthermore,this increased cable passageway allows the preload bolt to be fullyremoved without disconnecting the bicycle brake cable from the frontbrake caliper adjustment assembly.

By configuring the hex socket off center from the axis of alignment ofthe preload bolt, it is possible to create a much wider brake cablerouting passage through the preload bolt than is possible inconventional preload bolt designs. This provides space for the brakecable to easily pass through the large brake cable routing opening nextto the hexagonal wrench socket. As a result, the hexagonal socket isnever blocked and can be the sole means of adding bolt tension. Becausethe external wrench flats are no longer required, this constructionallows the outer profile of the bolt to be much lower and smoother.Furthermore, the brake cable routing passage can be large enough toaccept the larger parts of the brake cable assembly so that servicingand part replacement can be preformed without disassembling the brakecable assembly from the front brake caliper.

The invention may be described with greater clarity and particularity byreference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side elevational view illustrating the combination of abicycle front wheel fork and steering tube of the invention as mountedin position on a bicycle.

FIG. 2 is an exploded, front elevational view of the bicycle fork andsteering tube assembly of the invention.

FIG. 2A is a sectional elevational detail taken along the lines 2A-2A inFIG. 2.

FIG. 3 is a side elevational view of the bicycle fork and steering tubeof the invention.

FIG. 4 is a front elevational view, partially broken away, of a singleone of the bicycle fork legs employed in the invention.

FIG. 5 is an inside side elevational view showing the bicycle fork legof FIG. 4 in isolation.

FIG. 6 is a front elevational view illustrating the bicycle steeringtube shown in isolation.

FIG. 7 is a side sectional view showing the bicycle steering tube inisolation and prior to deformation of the dropout tabs thereof.

FIG. 8 is a perspective view showing the dropout support insert of theinvention in isolation.

FIG. 9 is a side elevational view of the dropout support insert shownFIG. 8.

FIG. 10 is a front elevational view of the bicycle dropout insert takenalong the lines 10-10 in FIG. 9.

FIG. 11 is a top plan view of the bicycle dropout insert taken along thelines 11-11 in FIG. 9.

FIG. 12 is a bottom plan view of the bicycle fork and steering tubeassembly of the invention.

FIG. 13 is a sectional elevational view of the hollow, cylindrical,annular preload bolt employed in the invention.

FIG. 14 is a perspective view showing the preload bolt of the inventionin isolation.

FIG. 15 is a top plan view of the bicycle preload bolt shown in FIG. 14.

FIG. 16 is a side elevational view of the bicycle preload bolt of theinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of presently-preferred embodimentsof the invention and is not intended to represent the only forms inwhich the present invention may be constructed or utilized. Thedescription sets forth the functions and the sequence of steps forconstructing and operating the invention in connection with theillustrated embodiments. However, it is to be understood that the sameor equivalent functions and sequences may be accomplished by differentembodiments that are also intended to be encompassed within the spiritand scope of the invention.

FIG. 1 illustrates the front portion of a BMX bicycle 10, which includesa conventional bicycle framework illustrated partially in phantom at 12,a front bicycle wheel illustrated in phantom at 14, and the combinationof a bicycle fork and steering tube assembly indicated generally at 16in FIG. 2. The assembly 16 includes a bicycle front wheel fork 18 and asteerer tube 20, both shown in FIG. 2. As in conventional BMX bicycles aclamping stem assembly 22 is provided to secure the bicycle steerer tube20 to the bicycle handlebars, indicated in phantom at 24.

The bicycle frame 12 is formed of tubular, rigid members including foreand aft frame members 26 and 28 which are welded to an upright bicycleframe head tube 30. The bicycle frame head tube 30 is a hollow,cylindrical structure that receives the bicycle steerer tube 20coaxially therewithin. The bicycle steerer tube 20 is freely rotatablewithin the laterally surrounding confines of the frame head tube 30.

The structure of the bicycle fork and steering tube assembly 16 isillustrated in detail in FIGS. 2 through 12. As illustrated in FIGS. 2,2A, 3, 6, 7, and 12, the bicycle fork assembly 16 is formed of thehollow steerer tube 20 that has an internally threaded upper end 31 anda lower end 32 at which a radially outwardly protruding headset bearingseat 34 is formed.

As shown in FIG. 7, a pair of diametrically opposed notches 36 isdefined in the lower end 32 of the steerer tube 20. The notches 36 aredirected concave upwardly toward the headset bearing seat 34 and have agenerally parabolic shape, as illustrated in FIG. 7. The notches 36thereby define a pair of downwardly directed end closure tabs 38therebetween.

As illustrated in FIG. 6, the end closure tabs 38 narrow from proximatethe headset bearing seat 34 to distal extremities 40. In the finishedconstruction the distal extremities 40 of the end closure tab 38 arebent in toward each other to meet in mutual abutment as indicated at thedemarcation 42 therebetween in FIGS. 2A and 12. The distal extremities40 of the enclosure tabs 38 are rigidly secured together by weldingwhere they meet at 42, as illustrated in FIG. 12 and in FIG. 2A. Asillustrated in drawing FIG. 2A, when the enclosure tabs 38 are bent intoward each other to meet in mutual abutment, the notches 36 are closedat their lower ends to define a pair of peripherally enclosed, generallytear-shaped fork openings 44 at the lower end 32 of the steerer tube 20.Also as shown in FIG. 2A, a front brake cable access aperture 46 isdrilled through one of the end closure tabs 38 after the end closuretabs 38 are bent into abutment and welded together.

The front brake cable access aperture 46 is defined through the curvedwall structure of one of the end closure tabs 38 of the steerer tube 20.The brake cable access aperture 46 permits the lower end of the bicyclebrake cable 48, shown in FIGS. 1 and 13, to exit the lower end 32 of thesteerer tube 20. The lower end of the brake cable 48 is operativelyconnected to a front brake assembly 49 as shown in FIG. 1. The frontbrake assembly 49 is mounted upon brake mounting pins 51. The frontbrake assembly 49 may be any conventional caliper brake assembly. It maybe a brake assembly such as that described, for example, in U.S. Pat.No. 6,019,522, which is hereby incorporated by reference in itsentirety. The bicycle brake cable 48 is omitted from FIG. 2A so as toallow clearer illustration of the junction of the front wheel fork 18with the steerer tube 20.

The bicycle front wheel fork 18 is formed by a pair of elongated,hollow, tubular steel legs 50. The tubular fork legs 50 are configuredin mirror image relative to each other. The fork legs 50 each have anupper end 52 and a lower end 54. Each of the fork leg upper ends 52terminates in a steerer tube interface opening 56, indicated in FIG. 5.

The edges 58 at the upper end 52 of each fork leg 50 follow the surfacecontour on the outer, curved surfaces of the end closure tabs 38 at thelower end 32 of the steerer tube 20.

The edges 58 that define the steerer tube interface openings 56 residein direct contact with and are welded about their circumferences to theend closure tabs 38 of the steerer tube 20, as indicated by the weldlines 60 shown in FIGS. 2, 3, and 12.

The lower ends 54 of each of the fork legs 50 terminate in bicycle axledropout slots 62. As illustrated in FIG. 4, the lower ends 54 of each ofthe fork legs 50 are permanently deformed to define a pair of flat,mutually parallel dropout tabs 64. U-shaped dropout notches 65 aredefined in the dropout tabs 64. As shown in FIG. 4, the lower ends 54 ofthe fork legs 50 are bent to form corresponding downwardly converginginterior wall surfaces 66 and 68 above the dropout tabs 64.

A dropout support insert 70, illustrated in isolation in FIGS. 8 through11, is disposed within each of the lower ends 54 of each fork leg 50.Each dropout support insert 70 has a lower reinforcement portion 72sandwiched in between the dropout tabs 64 and an upper brace portion 74that has inboard and outboard surfaces 76 and 78, respectively. Thesurfaces 76 and 78 follow the contours of the converging interior forkleg wall surfaces 66 and exterior fork leg wall surfaces 68,respectively, of the lower ends 54 of the fork legs 50.

The lower reinforcement portion 72 of each dropout support insert 70 isconfigured as a flat, yoke-shaped structure having a central, invertedU-shaped region 80 that conforms to the shape of the dropout notches 65.Upturned feet 82 reside in abutment against the edges 84 that arelocated between the spaced apart dropout tabs 64 at the lower ends 54 ofthe fork legs 50. The upturned feet 82 extend upwardly and in oppositedirections from the inverted, U-shaped section 80 and reside in abutmentagainst the lower edges 84 between the dropout tabs 64 in the lower forkleg ends 54. The upper, brace portion 74 of each dropout support insert70 resides in abutment against the converging interior wall surfaces 66and 68 in the lower ends 54 of the fork legs 50 above the dropout tabs64 thereof. To reduce weight a hole 75 is formed in the upper braceportion 74.

The dropout support insert 70 is further comprised of a stem 86 thatextends between the lower reinforcement portion 72 and the upper braceportion 74 of each dropout support insert 70. The brace portion 74 hasopposed upwardly diverging fork leg contact edges 76 and 78 that arealigned in a plane 90, indicated in FIG. 11, that is oriented at rightangles to the flat, yoke-shaped structure of the lower reinforcementportion 72, as illustrated in FIG. 11.

Narrow slits 67 are defined in each of the lower ends 54 of the forklegs 50 extending upwardly from the dropout notches 65 formed in thedropout tabs 64. The slits 67 are present to more readily allowdeformation of the lower ends 54 of the fork legs 50 to create themutually parallel dropout tabs 64. The slits 67 also allow the legs tobe welded to the inserts 70 along these lines to consolidate thestructure. The dropout support inserts 70 are installed in position inthe lower ends 54 of the fork legs 50 prior to deformation of the lowerfork leg ends 54 to create the dropout tabs 64. The lower ends 54 ofeach of the fork legs 50 are permanently deformed to define the pair offlat, mutually parallel tabs 64 disposed in spaced separation from eachother. The edges 76 and 78 of the upper, brace portion 74 of the dropoutsupport inserts 70 are aligned with the slits 67.

Once the lower ends 54 have been deformed so that the dropout tabs 64are pressed against the opposing flat surfaces of the yoke-shaped lowerdropout reinforcement portion 72, the lower reinforcement portion 72 ofthe dropout support insert 70 is welded to the dropout tabs 64 at thelower ends 54 of the fork legs 50. The lower ends 54 are also welded sothat weld material flows into the slits 67 to create a welded surfacebetween the inboard and outboard edges 76 and 78 of the upper braceportion 74 of the dropout inserts 70 and the curved, interior wallsurfaces 66 and 68 of the lower ends 54 of the fork legs 50.

The lower dropout reinforcement portion 72 of the dropout insert 70 issandwiched in between and welded to the dropout tabs 64. The inboard andoutboard edges 76 and 78, respectively, of the upper brace portion 74 ofthe dropout insert 70 follow the contours of the converging interiorwall surfaces 66 and 68, respectively.

The bicycle fork and steering tube assembly 16 of the invention isprovided with a preload bolt 100 at the upper end of the steerer tube20. The preload bolt 100 is a hollow, cylindrical, annular structurethat has an outer barrel 102 with external threads 104 defined thereonfor engagement with the conventional internally threaded upper end 31 ofthe steerer tube 20.

The upper end of the hollow, preload bolt 100 terminates in a narrow,radially outwardly directed flange 101. The barrel portion 102 of thepreload bolt 100 passes through the central, axial opening of a preloadwasher 103 so that the threads 104 on the exterior wall surface of thepreload bolt 100 are inserted into the hollow, central structure of theupper end 31 of the steerer tube 20. As the preload bolt 100 istightened, the preload washer 103 is compressed between the stem 22 andthe flange 101 at the top of the preload bolt 100.

The preload bolt 100 is provided with an interior dividing wall 106 thatdefines an upwardly facing wrench socket 108, as shown in FIGS. 13through 15. The wrench socket 108 is radially offset from axialalignment with the external threads 104 on the preload bolt barrel 102so as to delineate a relatively large brake cable routing passage 110within the hollow preload bolt 100.

As illustrated in FIG. 13, the wrench socket 108 defines an upperhexagonal region 114 and a lower hexagonal region 116 of smallercross-sectional area than the upper hexagonal region 114. The upper andlower regions 114 and 116 of the socket 108 accommodate different sizesof hex head wrenches, one of which is indicated in phantom at 118 inFIG. 13. For example, the upper hexagonal-shaped socket region 114 mayaccommodate an eight millimeter hex head wrench 118, while the lowerhexagonal-shaped socket region 116 may accommodate a smaller hex headwrench, such as a six millimeter wrench 118.

As is evident from FIG. 15, the vertical tip of a hex head wrench 118can be inserted down into the appropriate size socket region 114 or 116.As is evident from FIGS. 13 through 15, the hex head wrench 118 can beused to rotate the hollow preload bolt 100 about the axial center of thepreload bolt 100. The hex head wrench 118 is used to rotate the preloadbolt 100 about its own axis so that the socket 108 travels in an orbitalpath about the axis of the preload bolt barrel 102 as the preload bolt100 is tightened or untightened.

Due to the creation of the relatively large brake cable routing passage110 that is defined longitudinally through the structure of the preloadbolt 100 by the interior dividing wall 106, the entire preload bolt 100can be rotated to tighten it or loosen it relative to the upper end 31of the steerer tube 20 without disturbing the front bicycle brake cable48. That is, as the preload bolt 100 is rotated to tighten it into theupper end 31 of the steerer tube 20, the socket 108 is moved in anorbital, clockwise path, as viewed in FIG. 15, yet the front bicyclebrake cable 48 is not rotated, but merely moves laterally in an orbitalpath opposite the path of movement of the socket 108. As a consequence,the preload bolt 100 can be tightened and loosened without disturbingthe end connections of the front bicycle cable 48.

The bicycle fork and steering tube combination 16 of the presentinvention provides significant advantage over conventional structures.By forming the peripherally enclosed fork openings 44 at the lower end32 of the steerer tube 20, material is removed and weight is saved inthe construction of the steerer tube 20. This is accomplished withoutweakening the structure of the steerer tube 20, since the materialremoved at the notches 36 does not bear any great load. Furthermore, theclosed-off end of the steerer tube is thinner in section. However, dueto its closed shape it is less prone to distortion than a customaryopen-ended round tube. Therefore this thinner closed-off section canwithstand higher stresses with less distortion, while saving weight.

By providing the dropout slot 62 for the front wheel axle 63 directly inthe structure of the lower ends 54 of the fork legs 50, material issaved since no dropout mounting flanges are required. Moreover, thesystem avoids torsional stresses created by the offset between the forkleg tube axis and the axle position that would otherwise exist whenseparate dropout flanges, offset from the tube axis, are employed.

Additionally, by employing a tightening socket 108 radially offset fromthe axis of alignment of the preload bolt 100, a much larger bicyclebrake cable routing passage 110 can be defined through the hollow bolt100. Furthermore, the weight of providing external wrench flats on thepreload bolt flange 101 is avoided, thus allowing a significant weightreduction for the preload bolt 100. Moreover, the radially offsetlocation of the hex head wrench socket 108 permits a brake cable routingpassage 110 of much greater cross-sectional area to be formed in thepreload bolt 100 than would otherwise be possible. This largerpassageway also allows for a significant amount of weight to be saved.

A further benefit of the new design of the invention is that the preloadbolt can be completely removed from the fork steerer tube after thebrake cable lever lug has been unseated from the front brake lever. Thisis a simple step that can usually be accomplished without tools. Thepreload bolt can then slide easily up and over the large brake cablelever lug because of the unusually large cable passageway through thebolt. At this point disassembly and removal of the other bicyclecomponents (stem, headset, frame, fork, etc.) is more easily managed.With most traditional preload bolts, the lack of a large cablepassageway means that the cable has to be disassembled at the brakecaliper. This means that the user will have to lose all previousadjustment on the front brake caliper in order to pull the small“lugless” caliper-end of the cable up through the steerer tube and outfrom the conventional preload bolt to allow for the general removal ordisassembly of the other bicycle components in this area.

With both the new design and conventional designs basic brake adjustmentcan be made without disconnecting the brake. The major differencebetween the prior art and the present invention is the area of cabledisconnection when it comes to fully removing the preload bolt and thusthe other components from the steering system of the bicycle.

Undoubtedly, numerous variations and modifications of the presentinvention will become readily apparent to those familiar with bicycleconstruction. For example, dropout support inserts of varying geometricshapes can be employed in place of the preferred embodiment of thedropout support insert 70 illustrated and described. Accordingly, thescope of the invention should not be construed as limited to thespecific embodiment described herein, but rather is defined in theclaims appended hereto.

INDUSTRIAL APPLICABILITY

This invention may be industrially applied to the development,manufacture, and use of bicycle forks and steering tubes with particularapplication to BMX bicycles.

1. A bicycle fork assembly comprising: (a) a hollow steerer tube havinga lower end at which a head tube seat is formed, and with diametricallyopposed notches defined in said lower end and directed concave upwardlytoward said head tube seat, thereby defining a pair of downwardlydirected end closure tabs therebetween that narrow from proximate saidhead tube seat to distal extremities, and said distal extremities ofsaid end closure tabs are bent in toward each other to meet in mutualabutment where they are rigidly secured together, so that said notchesdefine peripherally enclosed fork openings at said lower end of saidsteerer tube, and; (b) a pair of hollow tubular fork legs having upperand lower ends, and each of said fork leg upper ends terminates in asteerer tube interface opening having edges that follow the surfacecontour of said lower end of said steerer tube and which surround saidfork leg openings and reside in direct contact with and are welded abouttheir circumferences to said end closure tabs of said steerer tube, andsaid lower ends of said fork legs terminate in bicycle axle dropouts. 2.A bicycle fork assembly according to claim 1, wherein each peripherallyenclosed fork opening is generally tear-shaped.
 3. A bicycle forkassembly according to claim 1, wherein said distal extremities of saidend closure tabs are welded together.
 4. A bicycle fork assemblyaccording to claim 1, wherein a front brake cable access aperture isdefined through one of said end closure tabs.
 5. A bicycle fork assemblyaccording to claim 1, wherein said lower ends of each of said fork legsare permanently deformed to define a pair of flat, mutually paralleldropout tabs with dropout notches defined therein, and correspondingdownwardly converging interior wall surfaces above said dropout tabs,and further comprising a dropout support insert that has a lowerreinforcement portion sandwiched in between said dropout tabs, and anupper brace portion that follows the contours of said converginginterior wall surfaces of said lower ends of said fork legs.
 6. Abicycle fork assembly according to claim 5, wherein said lower dropoutreinforcement portion of said dropout support insert is configured as aflat, yoke-shaped structure having a central, inverted U-shaped regionthat conforms to the shape of said dropout notches and upturned feetthat extend upwardly and in opposite directions from said invertedU-shaped region, and which reside in abutment against said lower ends ofsaid fork legs between said dropout tabs.
 7. A bicycle fork assemblyaccording to claim 6, wherein said dropout support insert is furthercomprised of a stem extending between said reinforcement portion andsaid upper brace portion, and said upper brace portion has opposedupwardly diverging fork leg contact edges that are aligned in a planeoriented at right angles to said flat yoke-shaped structure.
 8. Abicycle fork assembly comprising: (a) a hollow steerer tube having aclosed lower end with a pair of diametrically opposed fork leg openingsdefined therein, and (b) a pair of hollow tubular fork legs having upperand lower ends, and said upper ends of said fork legs terminate insteerer tube interface openings that completely surround said fork legopenings, and said upper ends of said fork legs are welded to said lowerend of said steerer tube throughout the circumferences of said steerertube interface openings.
 9. A bicycle fork assembly according to claim8, wherein the fork leg opening is generally tear-shaped.
 10. A bicyclefork assembly according to claim 8, wherein said lower ends of each ofsaid fork legs are permanently deformed to define a pair of flat,mutually parallel dropout tabs disposed in spaced separation from eachother and with dropout notches defined therein, and correspondingdownwardly converging interior wall surfaces above said dropout tabs,and further comprising a dropout support insert that has a lower dropoutreinforcement portion sandwiched in between said dropout tabs, and anupper brace portion that follows the contours of said converginginterior wall surfaces.
 11. A bicycle fork assembly according to claim10, wherein said lower dropout reinforcement portion of said dropoutsupport insert is configured as a flat, yoke-shaped structure having acentral, inverted U-shaped region that conforms to the shape of saiddropout notches and upturned feet that extend upwardly and in oppositedirections from said inverted U-shaped region, and which reside inabutment against said lower ends of said fork legs between said dropouttabs.
 12. A bicycle fork assembly according to claim 11, wherein saiddropout support insert is further comprised of a stem extending betweensaid reinforcement portion and said upper brace portion, and said upperbrace portion has opposed upwardly diverging fork leg contact edges thatare aligned in a plane oriented at right angles to said flat yoke-shapedstructure.
 13. A bicycle fork assembly according to claim 10, whereineach of said dropout support inserts are housed entirely within saidlower ends of each of said respective fork legs.
 14. A method ofconstructing a bicycle fork assembly, comprising: (a) providing a hollowsteerer tube having a lower end at which a head tube seat is formed; (b)creating diametrically opposed notches in said lower end and directedconcave upwardly toward said head tube seat, thereby defining a pair ofdownwardly directed end closure tabs therebetween that narrow fromproximate said head tube seat to distal extremities; (c) bending saiddistal extremities of said end closure tabs toward each other to meet inmutual abutment; (d) securing together said distal extremities so thatsaid notches define peripherally enclosed fork openings at said lowerend of said steerer tube, and; (e) providing a pair of hollow tubularfork legs having upper and lower ends, and each of said fork leg upperends terminating in a steerer tube interface opening having edges thatfollow the surface contour of said lower end of said steerer tube andwhich surround said fork leg openings and reside in direct contact withtheir circumferences; (f) securing said end closure tabs of said steerertube about said respective hollow tubular fork leg.
 15. A method ofconstructing a bicycle fork assembly according to claim 14, wherein eachnotch is generally tear-shaped.
 16. A method of constructing a bicyclefork assembly according to claim 14, further comprising welding saiddistal extremities of said end closure tabs.
 17. A method ofconstructing a bicycle fork assembly according to claim 14, furthercomprising forging a front brake cable access aperture through one ofsaid end closure tabs.
 18. A method of constructing a bicycle forkassembly according to claim 14, further comprising: (a) permanentlydeforming said lower ends of each of said fork legs to define a pair offlat, mutually parallel dropout tabs with dropout notches definedtherein, and corresponding downwardly converging interior wall surfacesabove said dropout tabs, (b) providing a dropout support insert that hasa lower reinforcement portion and an upper brace portion that followsthe contours of said converging interior wall surfaces of said lowerends of said fork legs, and (c) sandwiching said dropout support insertin between said dropout tabs.
 19. A method of constructing a bicyclefork assembly according to claim 18, wherein said lower reinforcementportion of said dropout support insert is configured as a flat,yoke-shaped structure having a central, inverted U-shaped region thatconforms to the shape of said dropout notches and upturned feet thatextend upwardly and in opposite directions from said inverted U-shapedregion, and which reside in abutment against said lower ends of saidfork legs between said dropout tabs.
 20. A method of constructing abicycle fork assembly according to claim 19, wherein said dropoutsupport insert is further comprised of a stem extending between saidlower reinforcement portion and said upper brace portion, and said upperbrace portion has opposed upwardly diverging fork leg contact edges thatare aligned in a plane oriented at right angles to said flat yoke-shapedstructure.